1. Field of Invention
The present invention relates to an electronic system and an alarm device thereof.
2. Related Art
Functional requirements of an electronic apparatus are getting higher, and more accessory apparatuses are required by the electronic apparatus to satisfy the multi-functional requirement. Usually, a processor controls the electronic apparatus for the purpose of driving, controlling, detecting, indicating and communication transmitting.
Referring to FIG. 1, a conventional system 1 has a micro control unit (MCU) 12, a speed detecting end 13 and a fan 14. The micro control unit 12 is electrically connected to the electronic device, such as a fan, and the speed detecting end 13 for detecting the rotating speed of the fan 14.
According to an external input signal S01, the conventional micro control unit 12 can output a control signal S02 to control the fan 14. Herein, the external input signal S01 can be a pulse width modulation (PWM) signal, which is composed of at least one high-level digital signal and at least one low-level digital signal. The micro control unit 12 can control the fan 14 operating at a normal status, such as the fan operates at a certain rotating speed, according to the external input signal S01 (PWM signal).
If the micro control unit 12 has malfunction or damage in hardware due to the unknown external factors, it may continuously control the fan 14 operating at the high-speed or low-speed rotation status for a long time. This may cause the damage of the fan 14.
When the micro control unit 12 has malfunction or damage in hardware, it can not correctly control the operation of the fan 14 for dissipating heat. Therefore, the fan 14 can not perform the heat dissipation efficiently, and if this problem goes worse, the entire electronic apparatus may be shut down.
Moreover, the micro control unit 12 has a control interface (not shown), which is connected with a connector (not shown), so that the external input signal S01 can be inputted to the micro control unit 12 through the connector and the control interface. When the fan 14 operates normally, and the connector and the control interface are not perfectly connected or the connection therebetween is loosen due to vibration caused by the external force, the micro control unit 12 can not receive the external input signal S01. Thus, the fan 14 will keep operating. That is, the micro control unit 12 can not stop the operation of the fan 14 in this case, which may cause the extra power consumption and damage of the fan 14.